Three-dimensional printing device

ABSTRACT

A 3D printing device, which is adapted to print a second object on a first object. The 3D printing device includes a body, a 3D printing unit, a sensor unit, a storage unit, a control unit and a carrier plate. The control unit is electrically connected to the 3D printing unit, the storage unit and the sensor unit. The storage unit stores initial coordinates, and the initial coordinates correspond to an initial printing position of the 3D printing unit. The carrier plate is located at a bottom of the body and has a ocular mark. The first object is adapted to be placed on the carrier plate. The sensor unit senses a height of the first object relative to the carrier plate, and the control unit drives the 3D printing unit to print the second object on the first object according to the height and the initial coordinates.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the priority benefit of Chinese applicationserial no. 201510002852.9, filed on Jan. 5, 2015. The entirety of theabove-mentioned patent application is hereby incorporated by referenceherein and made a part of this specification.

BACKGROUND

1. Technical Field

The disclosure relates to a three-dimensional (3D) printing device.

2. Related Art

In recent years, along with quick development of technology, differentmethods for constructing physical three-dimensional (3D) models by usingan additive manufacturing technology are provided. Generally, theadditive manufacturing technology is to convert design data of the 3Dmodel constructed by software such as computer aided design (CAD), etc.into a plurality of consecutively stacked thin (quasi-2D)cross-sectional layers. Meanwhile, a plurality of technical methods forforming the thin cross-sectional layers are gradually developed. Forexample, a printing unit of the 3D printing device can move above aprinting platform along an XY-plane according to special coordinates XYZconstructed according to the design data of the 3D model, such that aconstructing material can form a correct shape of the cross-sectionallayer. Then, the printing unit is driven to move layer-by-layer along aZ-axis, and the cross-sectional layers can be consecutively stacked toform a 3D object after curing layer-by-layer.

However, when a second object is to be printed on a first object, how toeffectively place the first object in the 3D printing area to avoidmisalignment such as skew or offset occurred during the 3D printingprocess has to be considered by related practitioners.

SUMMARY

The disclosure is directed to a three-dimensional (3D) printing device,where a user can easily perform object alignment through a ocular mark.

The disclosure provides a 3D printing device, which is adapted to printa second object on a first object. The 3D printing device includes abody, a 3D printing unit, a sensor unit, a storage unit, a control unitand a carrier plate. The control unit is electrically connected to the3D printing unit, the storage unit and the sensor unit. The storage unitis used for storing initial coordinates, and the initial coordinatescorrespond to an initial printing position of the 3D printing unit. Thecarrier plate is located at a bottom of the body and has a ocular mark.The first object is adapted to be placed on the carrier plate. Thesensor unit is controlled by the control unit to sense a height of thefirst object relative to the carrier plate, and the control unit drivesthe 3D printing unit to print the second object on the first objectaccording to the height and the initial coordinates.

The disclosure provides a 3D printing device, which is adapted to printa second object on a first object. The 3D printing device includes abody, a 3D printing unit, a sensor unit, a storage unit, a control unit,a carrier plate and a mark medium. The storage unit stores initialcoordinates, where the initial coordinates correspond to an initialprinting position of the 3D printing unit. The carrier plate is locatedat a bottom of the body. The first object is adapted to be placed on thecarrier plate. The control unit is electrically connected to the 3Dprinting unit, the storage unit and the sensor unit. The mark medium hasan ocular mark, and the ocular mark indicates a corresponding positionof the initial coordinates. The sensor unit is controlled by the controlunit to sense a height of the first object relative to the carrierplate, and the control unit drives the 3D printing unit to print thesecond object on the first object according to the height and theinitial coordinates.

According to the above descriptions, in the aforementioned embodiment ofthe disclosure, the carrier plate has the ocular mark, and the ocularmark is used for indicating a corresponding position of the initialcoordinates of the 3D printing unit, the user can place the first objecton the carrier plate and align the first object through the ruler scale.Meanwhile, the sensor unit senses the height of the first object, suchthat the 3D printing device obtains a spatial position of the firstobject, and accurately prints the second object on the first objectduring the 3D printing. In this way, the device is unnecessary toadditionally calculate the relative position of the first object, suchthat the time and cost of the 3D printing are effectively saved.

In order to make the aforementioned and other features and advantages ofthe disclosure comprehensible, several exemplary embodiments accompaniedwith figures are described in detail below.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings are included to provide a furtherunderstanding of the disclosure, and are incorporated in and constitutea part of this specification. The drawings illustrate embodiments of thedisclosure and, together with the description, serve to explain theprinciples of the disclosure.

FIG. 1 is a schematic diagram of a 3D printing device according to anembodiment of the disclosure.

FIG. 2 is a partial top view of a bottom of the 3D printing device ofFIG. 1.

FIG. 3 is a schematic diagram of an electrical connection of a part ofcomponents in the 3D printing device of FIG. 1.

FIG. 4 is a flowchart illustrating a 3D printing process according to anembodiment of the disclosure.

FIG. 5 is a partial top view of a carrier plate of a 3D printing deviceaccording to another embodiment of the disclosure.

FIG. 6 is a partial top view of a carrier plate of a 3D printing deviceaccording to another embodiment of the disclosure.

FIG. 7 is a schematic diagram of a 3D printing device according toanother embodiment of the disclosure.

FIG. 8 is an exploded view of the 3D printing device of FIG. 7.

FIG. 9 is a schematic diagram of a 3D printing device according toanother embodiment of the disclosure.

FIG. 10 is a schematic diagram of an electrical connection of the 3Dprinting device of FIG. 9.

FIG. 11 is a schematic diagram of a 3D printing device according toanother embodiment of the disclosure.

FIG. 12 is a schematic diagram of an electrical connection of the 3Dprinting device of FIG. 11.

FIG. 13 is a schematic diagram illustrating alignment of a 3D printingdevice according to another embodiment of the disclosure.

DETAILED DESCRIPTION OF DISCLOSED EMBODIMENTS

FIG. 1 is a schematic diagram of a 3D printing device according to anembodiment of the disclosure. FIG. 2 is a partial top view of the bottomof the 3D printing device of FIG. 1. FIG. 3 is a schematic diagram of anelectrical connection of a part of components in the 3D printing deviceof FIG. 1. Referring to FIG. 1 to FIG. 3, in the present embodiment, the3D printing device 100 is adapted to print a second object 20 on a firstobject 10. The 3D printing device 100 includes a body 110, a 3D printingunit 120, a sensor unit 130, a control unit 140, a carrier plate 150 anda storage unit 160. The control unit 140 is electrically connected tothe 3D printing unit 120, the storage unit 160 and the sensor unit 130.The carrier plate 150 is located at a bottom of the body 110, and thestorage unit 160 is used for storing initial coordinates, and theinitial coordinates correspond to an initial printing position of the 3Dprinting unit 120 in the body 110, and the carrier plate 150 has anocular mark for indicating the corresponding position of the initialcoordinates. In the present embodiment, the ocular mark is, for example,a ruler scale 152 on the carrier plate 150. The first object 10 isadapted to be placed on the carrier plate 150. The sensor unit 130 iscontrolled by the control unit 140 to sense a height of the first object10 relative to the carrier plate 150, and the control unit 140 drivesthe 3D printing unit 120 to print the second object 20 on the firstobject 10 according to the height and the aforementioned initialcoordinates.

In detail, the body 110 includes a plurality of guide rods 112 a-112 dset on the bottom, a pair of brackets 114 a and 114 b, a connection rod116 connected between the pair of the brackets 114 a and 114 b, and aplurality of driving units 118 a-118 e electrically connected to thecontrol unit 140. The brackets 114 a and 114 b respectively sleeve theguide rods 112 a-112 d, and the driving units 118 a and 118 b arelocated at opposite sides of the carrier plate 150 and respectivelyinclude a motor A1 and a screw rod A2, where the motor A1 is disposed onthe bottom of the body 110, and the screw rod A2 extends along a Z-axisand is coupled to the motor A1 and is driven by the same to rotate. Thebrackets 114 a and 114 b are connected to the screw rods A2 at twosides, and are adapted to move along the Z-axis. The driving units 118 cand 118 d are respectively disposed on the brackets 114 a and 114 b fordriving the connection rod 116 and the 3D printing unit 120 thereon tomove back and forth along a Y-axis. The driving unit 118 e is disposedon the connection rod 116 for driving the 3D printing unit 120 to movealong an X-axis. The 3D printing unit 120 includes a material barrel 122and a driving unit 124, where the material barrel 122 is used forcontaining a printing material, and is movably disposed on theconnection rod 116 through the driving unit 118 e, and when the materialbarrel 122 moves to a specific position, the driving unit 124 iscontrolled by the control unit 140 to squeeze the printing material on aplane of the first object to form the second object 20.

In the present embodiment, the 3D printing unit 120 is adapted toimplement 3D printing of food serving as the printing material, i.e. thefirst object 10 and the second object are all food. For example, throughthe 3D printing unit 120 of the disclosure, a plurality of creampatterns (i.e. the second object 20) can be printed on a cake base (i.e.the first object 10). However, as described above, since the secondobject 20 is not directly printed on the carrier plate 150, a positionof the first object 10 in the body 110 has to be confirmed in order toaccurately print the second object 20 on the first object 10.

Therefore, FIG. 4 is a flowchart illustrating a 3D printing processaccording to an embodiment of the disclosure. Referring to FIG. 4, andFIG. 1 to FIG. 3, in step S110, the first object 10 is placed on thecarrier plate 150. Then, in step S120, the first object 10 is aligned tothe ruler scale 152 on the carrier plate 150. In step 130, the sensorunit 130 senses a height of a top plane S1 of the first object 10relative to the carrier plate 150 (i.e. a plane where the ruler scale152 is located). It should be noticed that the sensor unit 130 includesan emitter A3 and a receiver A4 respectively disposed on the brackets114 a and 114 b, and determines a height difference between the topplane S1 of the first object 10 and the plane where the ruler scale 152is located, so as to determine a relative position that the drivingunits 118 a and 118 b control the 3D printing unit 120 along the Z-axis.The type and configuration position of the sensor unit 130 on the body110 are not limited by the disclosure, and as long as a sensor of theexisting technique is capable of sensing the height of the first object10 disposed on the carrier plate 150, it is considered to be adapted tothe present embodiment.

Finally, in step S140, the 3D printing device 100 is started, andaccording to the aforementioned collected information, i.e. the heightof the top plane S1 of the first object 10 relative to the carrier plate150, the control unit 140 controls the 3D printing unit 120 to print thesecond object 20 on the first object 10 according to the height and theinitial coordinates. It should be noticed that since the first object 10has been placed on the carrier plate 150 and is aligned through theruler scale 152, the 3D printing device 100 is only required tocorrespondingly set the specific position of the first object 10corresponding to the ruler scale 152, and according to theaforementioned sensed height, the 3D printing unit 120 can print thesecond object 20 within the required range on the XY-plane. For example,as shown in FIG. 2, the first object 10 is placed within a scale 5 ofthe ruler scale 152, when the 3D printing is performed, the 3D printingunit 120 is only required to perform the 3D printing within the range ofthe scale 5. Therefore, the 3D printing device is unnecessary toadditionally align and set the first object 10, which saves a time ofthe 3D printing.

However, a relative relationship between the first object and the rulerscale is not limited by the disclosure, which can be correspondingly setaccording to a contour and a size of the first object. In other words,the initial coordinates (the initial printing position) of the 3Dprinting unit 120 can be any position on the ocular mark (i.e. the rulerscale 152 of the present embodiment), and in the aforementionedembodiment, the initial coordinates correspond to a reference point C1of the ruler scale 152 (i.e. a center point with a scale of 0), andsince the first object 10 has a symmetric contour, a shape center of thefirst object 10 is located on the reference point 10, such that thefirst object 10 presents a symmetric contour relative to the referencepoint C1. In other words, the shape center of the first object 10 istaken as a reference point, and the reference point of the first object10 is adapted to the reference point of the ruler scale 152. Certainly,in other embodiments, to facilitate related operations, suitablemodifications can also be made. A shown in FIG. 2, a first object 30presents a fan shape, and an endpoint C2 of the first object 30 isaligned to the reference point C1, such that the first object 30 islocated in one quadrant of the ruler scale 152, i.e. now the endpoint C2of the first object 30 is taken as the reference point. Therefore, the3D printing unit 120 is only required to perform the 3D printing withreference of the above quadrant of the ruler scale 152, and the secondobject (not shown) can be successfully formed on the first object 30.Therefore, by forming the aforementioned relative relationship betweenthe reference point of the first object and the reference point of theruler scale 152, the control unit 140 can control the 3D printing unit120 to print the second object on the first object according to theaforementioned relative relationship.

FIG. 5 is a partial top view of a carrier plate of a 3D printing deviceaccording to another embodiment of the disclosure. Referring to FIG. 5,different to the aforementioned embodiment, the ruler scale 152 of theaforementioned embodiment presents a concentric circle pattern, whilethe ruler scale 252 of the present embodiment presents a concentricpolygon pattern (for example, a concentric quadrilateral), since thefirst object probably has a plurality of contours, the ruler scale 252on the carrier plate can also be varied along with the contour of thefirst object. As shown in FIG. 5, since a first object 40 is aquadrilateral, the quadrilateral ruler scale 252 is adopted, such that ashape center of the first object 40 can be successfully aligned to areference point C3 of the ruler scale 252 (i.e. a center point of theruler scale 252). Similarly, the user can also align an endpoint C4 of afirst object 50 to the reference point C3 of the ruler scale 252, oralign an endpoint C4 of the first object 50 to an endpoint C6 of theruler scale 252, so as to achieve an effect of aligning the first objectto the ruler scale.

Moreover, it should be noticed that in the embodiment of FIG. 2 and FIG.5, in order to facilitate recognizing the first object and the rulerscale, the dot line contour of the first object is misaligned to theruler scale in presentation.

FIG. 6 is a partial top view of a carrier plate of a 3D printing deviceaccording to another embodiment of the disclosure. In the aforementionedembodiment, regardless of whether an endpoint or the shape center of thefirst object is taken as the reference point, the reference point of thefirst object is coincided to the reference point of the ruler scale.However, different to the aforementioned embodiment, an origin point ofthe ruler scale 352 is taken as a reference point C7, and a first object60 has a reference point C8, where the reference points C7 and C8 has arelative displacement there between. For example, the reference point ofthe first object 60 is located at (3,3) of the ruler scale 352, therelative displacement can be represented by a vector D(3,3), and aprintable scope of the first object 60 is (−2˜+2, −2˜+2), so thatregarding the ruler scale 352, a printable scope of the 3D printing unit120 is (+1˜+5, +1˜+5), and the printable scope of the 3D printing unit120 is still smaller than or equal to an area of a top plane of thefirst object 60.

FIG. 7 is a schematic diagram of a 3D printing device according toanother embodiment of the disclosure. FIG. 8 is an exploded view of the3D printing device of FIG. 7. Referring to FIG. 7 and FIG. 8, thecomponents of the present embodiment that are the same to that of theaforementioned embodiment are not repeated, and a difference between thepresent embodiment and the aforementioned embodiment is that the carrierplate 350 of the 3D printing device 300 is detachably disposed on thebottom of the body 310. Further, the 3D printing device 300 of thepresent embodiment further includes a track 320 disposed on the bottomof the body 310, and the carrier plate 350 includes a first plate member352 and a second plate member 354 stacked to each other, where the firstplate member 352 is movably disposed on the track 320, and the secondplate member 354 is detachably positioned on the first plate member 352,and the second plate member 354 has a ruler scale 354 c.

It should be noticed that the first plate member 352 is a double layerstructure containing a substrate A5 and a carrier A6, where the carrierA6 is assembled to the substrate A5 through lock adjustment members 352a, such that when the carrier A6 and the substrate A5 are assembled, aheight of the carrier A6 relative to the substrate A5 can be adjustedthrough the lock adjustment members 352 a. Moreover, positioning polesA7 and A8 are set on the carrier A6, and the second plate member 354 hasa positioning hole 354 a and a positioning notch 354 b, such that bypositioning the positioning pole A7 to the positioning hole 354 a andpositioning the positioning pole A8 to the positioning notch 354 b, thesecond plate member 354 can be successfully positioned on the carrierA6. Therefore, through collaboration of the track 320 and the firstplate member 352, and based on a structural relationship between thefirst plate member 352 and the second plate member 354, the second platemember 354 having the ruler scale 354 c can be easily replaced. In thisway, the user can adopt various ruler scales 354 c by replacing thesecond plate member 354, by which an application scope of the 3Dprinting device 300 on the first object (not shown, and referring to theaforementioned embodiment for reference) can be expanded.

FIG. 9 is a schematic diagram of a 3D printing device according toanother embodiment of the disclosure. FIG. 10 is a schematic diagram ofan electrical connection of the 3D printing device of FIG. 9. Referringto FIG. 9 and FIG. 10, different to the aforementioned embodiment, adisplay 420 is set on the bottom of the body 410 of the 3D printingdevice 400 to replace the carrier plate and the ruler scale thereon inthe aforementioned embodiments. The display 420 is electricallyconnected to the control unit 140, and the first object 10 is adapted tobe placed on any position of the display 420. The display 420 displays aruler scale 452 to facilitate the user placing the first object 10 onthe display 420 and aligning to the ruler scale 452. In other words, theruler scale 452 of the present embodiment is substantially a virtualpattern, and the user is unnecessary to produce a physical carrier platein advance, and since the scope of the ruler scale is complied with theplane of the first object, and the contour of the ruler scale can becomplied with the contour of the first object, the user is unnecessaryto replace the carrier plate in allusion to different first objects asthat does in the aforementioned embodiment.

Then, once the first object 10 is aligned to the ruler scale 452 on thedisplay 420, as that described in the above embodiment, the sensor unit130 senses the height of the top surface S1 of the first object 10relative to the display 420, and the control unit 140 drives the 3Dprinting unit 120 to print the second object 20 on the top plane S1 ofthe first object 10 according to the information of the ruler scaledisplayed on the display 420 and the height of the first object 10.

FIG. 11 is a schematic diagram of a 3D printing device according toanother embodiment of the disclosure. FIG. 12 is a schematic diagram ofan electrical connection of the 3D printing device of FIG. 11. Differentto the aforementioned embodiment, the 3D printing device 500 furtherincludes a mark medium 520 disposed beside a body 510, and the markmedium 520 has an ocular mark 525 indicating a corresponding position ofthe initial coordinates of the 3D printing unit 120 (referring torelated referential number of FIG. 1). In this way, the user can placethe first object 10 on the carrier plate 150 (referring to relatedreferential number of FIG. 1) according to the position shown on themark medium 520. In the present embodiment, the mark medium 520 is, forexample, a display, which can display the ocular mark 525 of differentpatterns according to an actual requirement. In another embodiment thatis not shown, the mark medium can be a different medium used ofdisplaying various patterns such as a paper, etc.

FIG. 13 is a schematic diagram illustrating alignment of a 3D printingdevice according to another embodiment of the disclosure. In FIG. 13, apart of the components of the 3D printing device is omitted, and theembodiment of FIG. 1, FIG. 9 or FIG. 10 can be referred forimplementation. The embodiment of FIG. 1 is referred for reference, andthe related components and referential numbers of the present embodimentmay refer to the embodiment FIG. 1, which are not repeated. In thepresent embodiment, the 3D printing device further includes anindicating unit 170, which is disposed on the body 110 and electricallyconnected to the control unit 140. The indicating unit 170 is, forexample, an infrared laser, and displays an ocular mark C9 on thecarrier plate 150 in an optical manner, so as to facilitate the user toalign the first object 10 thereto. The present embodiment corresponds tothe aforementioned embodiments of FIG. 2 and FIG. 5, i.e. the indicatingunit 170 indicates the initial position on the ruler scale 152 to serveas an alignment reference for the first object 10.

In the present embodiment, since the carrier plate 150 already has apart of the ocular mark (i.e. the ruler scale 152), the indicating unit170 is only used for indicating the initial coordinates of the 3Dprinting unit. However, the disclosure is not limited thereto, an inanother embodiment that is not shown, when the carrier plate does nothave the aforementioned ruler scale, the indicating unit can display anocular mark having a 2D pattern on the carrier plate throughcorresponding configuration of a vibration mechanism (for example, ascan mirror or a vibration mirror), so as to facilitate alignment of thefirst object.

In summary, in the aforementioned embodiments of the disclosure, bysetting the carrier plate having the ruler scale at the bottom of thebody, the user can place the first object on the carrier plate and alignthe same according to the ruler scale, such that the first object andthe ruler scale have a relative relationship, and after the sensorsenses the height of the first object relative to the carrier plate,complete spatial information of the first object on the carrier plate isobtained. In this way, the 3D printing device can determine a position(i.e. spatial coordinates) of the top plane of the first objectaccording to the aforementioned relative relationship and the height,and can directly printing the second object on the first object.Therefore, based on the ruler scale on the carrier plate and the heightsensed by the sensor, the 3D printing device is unnecessary toadditionally sense and calculate the spatial position of the firstobject, namely, the user is only required to input a planar position ofthe first object on the carrier plate to the 3D printing device, bywhich the time required for implementing the 3D printing is effectivelysaved.

It will be apparent to those skilled in the art that variousmodifications and variations can be made to the structure of thedisclosure without departing from the scope or spirit of the disclosure.In view of the foregoing, it is intended that the disclosure covermodifications and variations of this disclosure provided they fallwithin the scope of the following claims and their equivalents.

What is claimed is:
 1. A three-dimensional printing device, adapted toprint a second object on a first object, the three-dimensional printingdevice comprising: a body; a three-dimensional printing unit, disposedon the body; a storage unit, storing initial coordinates, wherein theinitial coordinates correspond to an initial printing position of thethree-dimensional printing unit; a carrier plate, located at a bottom ofthe body, and having a ocular mark, wherein the ocular mark indicates acorresponding position of the initial coordinates; a sensor unit; and acontrol unit, electrically connected to the three-dimensional printingunit, the storage unit and the sensor unit, wherein the sensor unit iscontrolled by the control unit to sense a height of the first objectrelative to the carrier plate, and the control unit drives thethree-dimensional printing unit to print the second object on the firstobject according to the height and the initial coordinates.
 2. Thethree-dimensional printing device as claimed in claim 1, wherein thefirst object has a plane, the second object is located on the plane, andthe sensor unit is used for sensing the height of the plane relative tothe carrier plate.
 3. The three-dimensional printing device as claimedin claim 1, wherein the ocular mark is a ruler scale, and the initialcoordinates are within a scope of the ruler scale.
 4. Thethree-dimensional printing device as claimed in claim 3, wherein theinitial coordinates correspond to a center point of the ruler scale. 5.The three-dimensional printing device as claimed in claim 3, wherein acontour of the ruler scale is complied with a contour of the firstobject.
 6. The three-dimensional printing device as claimed in claim 1,wherein the first object and the second object are food.
 7. Thethree-dimensional printing device as claimed in claim 1, wherein thecarrier plate is detachably disposed at the bottom of the body.
 8. Thethree-dimensional printing device as claimed in claim 7, furthercomprising: a track, disposed on the bottom of the body, wherein thecarrier plate comprises: a first plate member, movably disposed on thetrack; and a second plate member, detachably positioned on the firstplate member, and the second plate member have the ruler scale.
 9. Thethree-dimensional printing device as claimed in claim 1, the carrierplate is a display to show the ocular mark.
 10. The three-dimensionalprinting device as claimed in claim 1, further comprising: an indicatingunit, disposed on the body, and electrically connected to the controlunit, wherein the indicating unit displays the ocular mark on thecarrier plate in an optical manner.
 11. A three-dimensional printingdevice, adapted to print a second object on a first object, thethree-dimensional printing device comprising: a body; athree-dimensional printing unit; a storage unit, storing initialcoordinates, wherein the initial coordinates correspond to an initialprinting position of the three-dimensional printing unit; a carrierplate, located at a bottom of the body, wherein the first object isadapted to be placed on the carrier plate; a sensor unit; a controlunit, electrically connected to the three-dimensional printing unit, thestorage unit and the sensor unit; and a mark medium, having an ocularmark, wherein the ocular mark indicates a corresponding position of theinitial coordinates, the sensor unit is controlled by the control unitto sense a height of the first object relative to the carrier plate, andthe control unit drives the three-dimensional printing unit to print thesecond object on the first object according to the height and theinitial coordinates.
 12. The three-dimensional printing device asclaimed in claim 11, wherein the first object has a plane, the secondobject is located on the plane, and the sensor unit is used for sensingthe height of the plane relative to the carrier plate.
 13. Thethree-dimensional printing device as claimed in claim 11, wherein theocular mark is a ruler scale, and the ruler scale and the carrier platecorrespond to each other and scopes thereof coincide to each other. 14.The three-dimensional printing device as claimed in claim 13, whereinthe initial coordinates correspond to a center point of the ruler scale.15. The three-dimensional printing device as claimed in claim 11,wherein the mark medium is a display.